some questions on installing XP (bootcamp) for gaming

Hi guys, i'm thinking of installing XP via bootcamp in my MBP. I plan to just use XP for games, probably just 2 at a time.

1. What size of a partition would you recommend? Will 20GB be good enough? I'd like to keep it to a minimum since I do mostly photo work on my mac so I want to have a lot of space for photo editing.

Another option is to save up for a larger HDD.

I won't be installing anything, just max 2 games at a time. Not even Office. Example of games I'd like to install: Bioshock, Half Life 2, Witcher, Age of Empires

2. Do you recommend I install the updates on XP even it's just for gaming? i.e. SP3?

3. Suppose I get a larger HDD (probably a 250GB) and want to use it for my MBP, how do you suppose I go to migrating my system to it? Ideally I'd like to have my system exactly the same so I was thinking of cloning the drive to the newer/larger one, but what will happen to the XP partition?

edit:

4. I read a lot of people comparing different video drivers for XP. which ones would you recommend I install?

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